#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

int num[110];

int main () {
        int n;
        memset (num, 0, sizeof num);
        cin >> n;
        for (int i = 1; i <= n; i++) {
                int a;
                cin >> a;
                num[a]++;
        }
        int ans = 0;
        for (int i = 1; i <= 100; i++) {
                ans = max (ans, num[i] + num[i - 1]);
        }
        cout << ans << endl;
        return 0;
}